Finally, in order to explore the reduction in background by means of the \(\gamma \) -ray imaging capability of i-TED a discrimination analysis was made on an event-by-event basis. To apply the Compton technique only events in time coincidence between the S- and A-layers were considered (solid red curve in Fig. REF ). The main drawback of the time-coincidence mode is the drastic reduction of the detection efficiency. As a consequence of the small number of A-detectors used in the present prototype, only 8% of the events detected in the S-detector make a further interaction in the A layer. In future measurements, the use of four PSDs in the A- plane will help to enhance the efficiency in coincidence mode significantly (see Ref. [1]}).
